1. Field of the Invention
Electrolytes and lithium-ion batteries.
2. Brief Description of the Related Art
Due to their high energy density and operating potential, lithium-ion batteries have been widely adopted in portable electronics. However, to enable their implementation in traction applications, such as for electric vehicles, considerable improvements must still be made in terms of cost, energy and power density, manufacture, and safety. Advances in electrode chemistries as well as the separator are needed to meet those challenges. Currently, macroporous polymer membranes swelled with lithium salts dissolved in organic carbonates are utilized as the separator in lithium-ion batteries. The use of a liquid electrolyte restricts battery shape and processing, while also posing numerous safety problems, due to the potential leakage of corrosive liquids and the volatility and flammability of the electrolyte solvent.
Furthermore, the lack of rigidity for current battery separators precludes the use of solid lithium as an anode, because repeated cycling leads to lithium dendrites that can pierce the separator and cause cell failure. In contrast, a rigid, solid separator could inhibit lithium dendrite growth and allow the use of metallic lithium as an anode. Given the high theoretical capacity of lithium metal (3860 Ah/kg), and it's very negative reduction potential (−3.04 V vs. SHE), such an advance would enable tremendous gains in energy capacity.
Since the 1970s, salts dissolved in solid polyethers have been investigated as solid electrolyte materials. However, the low conductivities of such materials at room temperature (10−6 S/cm) currently prevent their use in battery applications. Other solid lithium electrolytes either display total conductivities that are also too low or are poorly compatible with the battery electrodes.